Please try the following steps to cleanly reinstall the mod:
1. Unsubscribe from the mod.
2. Start the game and go into the main menu (this will uninstall the mod properly)
3. Close the game
4. Subscribe to the mod (this will install the mod again)
5. Start the game and see if that fixed the issue

I tried the clean reinstall steps you suggested, but unfortunately, I'm still getting the same error

Its a weird error message, because it says that its trying to do arithmetic on a value, but the line it says doesnt do any arithmetic operations at all...
Can you check that you are on EID version 4.97 (Its at the top of the debug console, or on the first page of the EID MCM entry)
Also, does the error occur only for a specific character you are playing?
does it happen for any object it tries to describe?
does the error also occur, if you only have EID enabled, and all other mods disabled?

Thanks for the follow-up. I'm on EID version 4.97.
The error happens with any character and in all situations, not tied to specific objects. It also occurs with EID as the only mod enabled.
On my end, the EID overlay only appears when I hold TAB. When it does, it shows character info and picked-up items, but doesn't describe items currently in the room (like those on pedestals).
This started after a Repentance+ update some time ago. A full game reinstall didn't fix it.
Hope this helps. This has been an issue for me for quite a while now:(

then its even weirder, if it happens for everything and without any other mods...
Is the error message you have posted the exact same, or are there more lines to it?

If you want, you can join the discord server of our mod, and we can take a look at the issue via screensharing: https://discord.gg/gRg5UJdumy

I'm sorry that it's not really feasible for me to do the screenshare due to network and language barriers. The error message I sent ("PostRender" failed: ...) is indeed the complete one I see for this specific issue.
I'll try to look for other potential solutions or see if I can find any more detailed error information on my end. If I find anything useful, I'll let you know.
Thanks!

Dont worry.

What i just noticed is the path that the mod displayed in your error message "resources/scripts/features/" doesnt really look like how the game handles mods. it should say something like "../mods/external item descriptions_836319872/features/eid_api.lua"

Did you maybe have installed the mod manually some time ago? Maybe with that weird guide for Online Coop Mod support?
if yes, then that is the problem. Go into the game folder, and delete the "resources/scripts" folder. That will remove that special installation of the mod. Then you need to do the "Verify Integrity of Game files" step to redownload "resources/scripts" folder for the game correctly. you can find a guide on how to do that here: https://inxile.zendesk.com/hc/en-us/articles/115004662908

If that is not the case, you can also try to send the "log.txt" file of the game in here. you can find it here: C:\Users\[YourName]\Documents\My Games\Binding of Isaac Repentance+\log.txt

You were right! That fixed it. The mod's working perfectly now.
Thanks so much for your help!

glad it works now :) have fun with the mod